The purpose of playing this campaign is to have fun.
No jerks. If you are acting like jerk on game day, don't come. How do you know who is a jerk and who isn't? Those who violate the mission statement are jerks. Everyone should do their best to both have fun and support the fun for all other players. Those not having fun or and/or spoiling fun for others will be asked to leave the campaign.
Players are encouraged to add “flavor” wherever they can. A good description of your PC, painting miniatures, a detailed PC background, some in-character fiction, or even helping to flesh out the campaign world are all welcome to all players – not just GMs.
Let the players make choices. That's what the game is all about. No railroading. At the very least give the players the illusion of free will. Instead of saying “no”, always consider saying “yes, but…”.
Try to keep adventure sessions reasonable in scope. Oftentimes even the best games can get too convoluted and out of hand if the GM tries to do too much. Try not to tackle “save the world” plotlines. “Save the nation” or “save the town” is about our speed. When in doubt, make the plot scope simply “save yourselves”.
GMs should count on writing a session log after each game they GM or convince someone else at the game session (a player/bystander/pet/etc) to write it for them. Example templates of logs can be forwarded to you at your request. A GM post-mortem and campaign polls are good to in order to gauge the feelings of the players, but are not necessary.